Roof water damage in the older San Marcos houses often starts at the chimney. Houses of that era were built with masonry chimneys, plenty of them no longer used for anything, and the chimney is the one place on a roof where three materials meet: brick, flashing, and roofing. The flashing there is frequently older than the roof around it, because a re-roof does not always mean new counterflashing, and the mortar crown on top of the stack cracks through enough hot summers. Water gets in at the joint and, instead of dripping into an attic, runs down the outside of the brick inside the chase that boxes it in.
A chase is a closed vertical shaft running from the roof to the first floor. Water inside it does not spread out and announce itself. It wets framing at every level it passes and comes out at the bottom, which is why the stain shows on a first-floor ceiling or at the top of a first-floor wall in a house whose leak is thirty feet above it. The other reason it goes unnoticed is that nobody opens a chase. Between two tenants and two owners, a chimney leak can run for years.
Drying a shaft you cannot walk into
We start with the meter rather than the ceiling. Readings taken up the wall on each floor show how far the water travels and where it is standing, and infrared shows the cool column behind the finish. Then the chase gets opened where it has to be, usually at the top of the run and at the wet floor rather than everywhere in between. Wet insulation and anything holding water comes out, air gets moved through the shaft instead of across the face of the wall, and framing readings get taken daily until they line up with dry wood in the same house. Masonry dries slowly and we plan for that rather than pulling equipment the day the drywall reads dry. A roofer rebuilds the flashing and the crown. We take the inside.
- Readings taken on every floor the chase passes, before anything is opened
- The chase opened at the top of the run and at the wet floor, not the whole height
- Air moved through the shaft rather than across the face of the wall
- Masonry given the drying days it actually takes, with daily readings behind it

A chimney leak is easy to misfile as a plumbing problem, since it surfaces on a ceiling well away from the roof, so we rule out the supply and drain lines above that room before anybody gets on a roof. Call (512) 271-5099 and tell us which floor the stain is on and what the weather was doing before it appeared.










